Final results on ^82 Se double beta decay to the ground state of ^82 Kr from the NEMO-3 experiment

Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay ( 2νββ ) half-life of ^82 Se as T_1/2^2ν=[ 9.39 ± 0.17( stat ) ± 0.58( syst ) ] × 10^19 y under the single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is | M^2ν| = 0.0498 ± 0.0016 . In addition, a search for neutrinoless double beta decay ( 0νββ ) using 0.93 kg of ^82 Se observed for a total of 5.25 y has been conducted and no evidence for a signal has been found. The resulting half-life limit of T_1/2^0ν > 2.5 × 10^23 y (90% C.L. ) for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of ⟨ m_ν⟩ < ( 1.2-3.0) eV , where the range reflects 0νββ nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other 0νββ mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.